The field of this invention is that of edgeboard connectors for mounting printed circuit boards, and the invention relates more particularily to edgeboard connectors having large numbers of contacts adapted to make electrical connection to one or more printed circuit boards each having a relatively lesser number of contact pads.
When edgeboard connectors are mounted on large printed circuit boards to permit a number of smaller printed circuit board units to be detachably mounted on the larger board by being inserted into the connectors, the connectors sometimes have contacts which exactly correspond in number to the contact pads provided at the edges of the smaller circuit board units. In that arrangement, when terminal portions of the connector contacts are soldered to circuit pads on the larger circuit boards and the smaller circuit boards are inserted into the connectors, the contact pads on the smaller units are easily mated with the correct contact means in the connectors. If neccessary, the smaller boards and the connectors sometimes have eccentrically disposed polarizing means such as grooves in the edges of the smaller boards which mate with thin ribs in the connectors only when the smaller boards are inserted into the connectors with the proper orientation of the top and bottom sides of the smaller board units.
However, in many printed circuit board systems, the connectors mounted on the larger circuit board have a much greater number of contacts than are necessary for making electrical connection to the number of contact pads at the edges of the small circuit board units to be mounted in the connector. Sometimes several of the smaller board units such as memory modules or the like are mounted in the same edgeboard connector. In such cases, when certain connector contacts are soldered to particular circuit pads on the larger board and when the smaller board units are inserted into the connectors, the connector contacts may be inadvertantly engaged with other than the intended contact pads on the smaller board units. In that regard, the contact pads are typically arranged at the edges of the smaller board units to have a standardized center-to-center spacing between the pads on the board units and they usually have a standardized end spacing between the lateral edges of the boards and contact pads adjacent to those lateral edges.